In this thesis the hydraulic influence between water level of Odra river and groundwater level of eastern part of Zagreb aquifer was determined. The analysis used data from piezometers B-153 and hydrological station Donja Poljana in the period from 1.1.2004. to 31.8.2012. In order to determine their relationship, three statistical methods were used: correlation method, regression method and cross correlation method. Data results are presented in the form of coefficient, diagram and correlogram in Microsoft Excel. The correlation method obtained correlation coefficient which shows weaker connection betwen water level of Odra river and grounwater levels of Zagreb aquifer. The regression method obtained low coefficient of determination indicating low reliability of groundwater level data used to forecast water level data of Odra river. The cross correlation method determined lag time between water level of Odra river and groundwater level of Zagreb aquifer.